1. Field of the Invention
This invention relates to wireless communication systems and, more particularly, to an improved antenna system.
2. Description of Related Art
Active antennas are commonly used where a connection cable between the antenna and the base transceiver have an unacceptable loss of signal. Active antenna systems solve this problem by amplifying the signal level before the lossy cable. Usually active antenna systems are utilized in low frequency, receive only applications. An active antenna system typically requires an RF signal line and a power supply line. For cost reduction purposes, current active antenna systems combine the power supply line and the signal line in one line, usually a coaxial cable. If switching between a transmit mode and a receive mode is required, the antenna system requires a separate control line to control the RxTx switching.
Antenna diversity is typically provided by antenna systems where the receiver selects a particular antenna out of a set of antennas. Antenna diversity assists in coping with multipath fading of a received signal whereby the signals received by each antenna are compared, and the antenna having the better reception or the best signal quality (for example, signal-to-noise ratio) as measured by the base transceiver is selected. A diversity antenna system requires additional control lines for antenna selection. A diversity antenna system is described in U.S. Pat. No. 5,420,599 to Erkocevic which provides antenna diversity in the receive mode. This diversity antenna system combines the control signals for switching between the transmit and receive modes and for antenna selection. This system uses extraneous control lines. Requiring separate wiring for control signals increases costs and reduces the modularity of the antenna system.
Thus, a need exists for an antenna system that overcomes the drawbacks of current systems in a cost effective manner.